davidson



R. J. DAVIDSON.

PROCESS OF REPRODUCING DESTRUCTIBLE OBJECTS BY CASTING.

AP LICATION FILED JAN-13,1915.

Patented Dec. 16, 1919.

2 SHEETSSHEET I.

a. J. DAVIDSON.-

PROCESS OF REPRODUCING DESTRUCTIBLE OBJECTS BY CASTING.

AP LICATION FILED JAN. 13, I915.

2 SHEETSSHEET 2.

Patented Dec. 16

ROBERT J'. DAVIDSON, OF ST. LOUIS, MISSOURI.

PROCESS OF REPRODUCING DESTRUGTIBLE OBJECTS BY CASTING.

Specification of Letters Patent.

Patented Dec. 16, 1919.

Application filed January 13. 1915. Serial No. 1,997.

To all whom it may concern:

Be it known that I, ROBERT J DAVIDSON, a citizen of the United States, residing at St. Louis, in the State of Missouri, have invented certain new and useful Improvements in Processes of Reproducing Destructible Objects by Casting, of which the following is a specification.

My invention relates to improvements in processes of reproducing destructible objects by casting.

In the operation of my invention a combustible pattern is invested in a suitable mixture of materials to form a porous mold around it, then this mold is dried and heated to burn out the pattern and leave a like'cavity therein, a metal is cast into this cavity, and then the materials of the mold removed from the casting thus formed.

The objects of my improvements are, first, to prevent the formation of ashes in the mold from the burning of the pattern,

second, to provide a'means for increasing the strength and thickness of thin or non rigid patterns, third, to prevent the forma-- tion' of protuberances on the casting and insure the proper copying of recesses, indentures and holes in the pattern, fourth, to insure the proper filling out of the mold by the metal cast therein.

I attain these objects, excepting the first, by means of the apparatus illustrated in the accompanying drawings in which Figure 1 shows a side View of a tool for applying wax to patterns.

Fig. 2 shows an end view of the tool shown in Fig. 1.

Fig. 3 represents a natural flower.

Fig. 4 shows a front view of the warming cabinet used in applying wax to patterns.

Fig. 5 shows a vertical section through the cabinet shown in Fig. 4 on the line ab.

Fig. 6 shows a vertical section of my improved flask seated upon the plate of the suction head shown in Fig. 12 Withra casti-ng. gate and sealing button therein.

Fig. 7 is a perspective view of the flask of Fig. 6 fastened to a suitable base by a thread wound over the two.

Fig. 81 is a vertical section of my device for investing a pattern with a mold mixture in a vacuum.

Fig. 9 shows a plan view of the collar between the parts of the receiver in Fig, 8.

Fig. 10 is an exterior view of the device shown in Fig. 8 connected to a gage and vacuum pump.

Fig. 11 shows the exterior of the flash holder shown in vertical section in Fig. 8. Fig. 12 is a "ertical section through the suction head used for casting in molds in combination with a base and pattern to which ,part of my improvements in reproducing objects may be applied.

Fig. 15 shows a vertical section through a base for adjustably mounting a pattern on a wire, or the stem thereof before union of this base; with a flask.

Fig. 16 shows a vertical section of a flask designed fto prevent a draft across the mold cavity when used for gaseous pressure casting;.a,rriodification of this flask is shown in r 1g. 17 shows a modification of the flask shown in 16 with holes gradually decreasing in size from near the top to'the bottom.

Fig. '18. shows a natural flower pattern stuck on the sharpened end of a piece of wire.

Fig. 19 shows a natural flower pattern stuck in the split end of a piece of wire.

Fig. 20 shows a vertical section of another vacuum investing device of different design from the one shown in Fig. 8.

Fig. 2l'shows a vertical section through slightly modified form of the device shown in Fig. 20.

Fig. 22 shows a vertical section of a modification of the base shown in Figs. 15 and 21; the turntable ball of this base has a hollow handle on the underside.

My improvements may each be used singly or any two or more of them together in my process of reproducing objects by casting according to the requirements of, or results desired, in any particular case.

In case the pattern is one which will leave when burned out enough ashes in the mold to cause flaws in the casting, and is not strong enough in all of its parts to insure it from being bent out of shape by the mold mixture when investing it therein, and not thick enough in all of its parts to form as thick a casting as desired, and that it is desired to prevent other faults from being formed in the mold and registering the casting, and to insure the proper filling of the mold by the metal cast therein, I first soak the pattern in a solution of hydrochloric acid in water until the ash forming ingredients which will combine with this acid are dissolved out; in case sil ceous matter is present in the ash forming ingredients of a pattern it is dissolved out by a further soaking of the pattern in a solution of hydrofluoric acid in water. After each soaking of the pattern in these acid solutions the pattern may be rinsed or soaked in water to remove the acids and their products from the pattern. In any case the acid solutions must be sufficiently diluted with water to prevent the vegetable matter of the pattern from being chemically attacked by the acid. Patterns of vegetable material which are wilted by soaking in acid solutions do not require to be soaked in these solutions, because such patterns seldom leave enough ash es in the mold cavity to cause flows in the casting produced therein, or only very small flaws. Other acid solutions may be substituted for the hydrochloric acid solution specific-ed above.

This pattern is next stuck onto the end of a piece of wire with Wax, this wire must be long enough for use as hereinafter described; it is first used as a handle by which to hold the pattern while applying melted wax thereto, unless, as is sometimes the case, it is found to be more convenient to hold the pattern in some other way as by the stem while applying the wax and then attach the wire afterward. A wax coating may be applied to a pattern by instruments ofvarious kinds which can be heated hot enough to melt the wax but not hot enough to wilt the pattern when held against it; the instrument shown in Figs. 1 and 2 is used for applying a coat of wax to a pattern. the metal ball 80 and pointed blade 81 are heated as above specified and the blade 81 is either dipped into melted wax or held against a solid piece of wax so as to get a covering of melted wax on the blade and point 81; the blade is then passed over the suri'ace to be coated and a part of the wax thereontransferred to the pattern. To fill a tubular part of a pattern, like the one shown in Figs. 3 and 14, and other cavities in other patterns a suitable small syringe may be used; the casting 1" of Fig. 6 may be thought of as one which has been made from a pattern with a short tubular part. Fig. 3 has been drawn for an aid to discussion and does not show directly where the wax is to be applied, in this case I do not intend to convey the idea that such a pattern cannot be reproduced without the application of wax, but to indicate with the aid of writing where wax can be applied to obtain a thicker and stronger casting; the tubular central portion 76 may be filled with wax to prevent a long slender core of mold material from being formed in this part such as would be apt to get broken off and interfere with the proper production of the pattern in the castmg. The filling of such a tubular portion might be the only application of wax desirable to make to this pattern, or it may be desired to also coat the backs of the petals 77, the stamens 7 8 and the stem 7 9 with wax, to make them larger and stronger than natural; or the petals of a flower which overlap may be wax coated and bent apart so that the petals of the casting will not be stuck together.

In Figs. 4 and 5 are shown two views of a cabinet for use in painting melted Wax onto a pattern with a brush; to operate this cabinet the tank Si is filled with water and the ]acket of the pot 90 is partly filled with water and a quantity of wax for use in coating the pattern is placed in the inside pot 90; the burner 91 is lighted to heat and melt the wax in the pot 90 and the burner 92 is lighted to *heat the tank 8% and its contents and the air in the box 82 over the tank. The evaporation of water from the wet bricks 86 keeps the air moist in the box 82. The patterns are placed in the tray 87 or in the front part of the box 82 by opening the lid 88. A person in applying a coat of wax to a pattern reaches into the box 82 through the holes 95 and applies a coating of wax to the pattern where it is desired, using a suitable short handled brush and observing the operation through the window 89; small patterns may be inserted or removed through the holes 95, larger patterns by opening the lid 88. v

The end of the aforesaid piece of wire, which so far has served as a handle to the pattern, 18 next passed through the cup 6 of the flask 6 shown in Fig. 6 and the hole in the bottom thereof and through the hole in a suitable base (not shown) which preferably fills the funnel 6, the wire is then adjusted through the base to bring the pattern into the position of the casting 1 of Fig. 6, and the part of the wire which extends below the base is cut ofi. The base 5 and the flask 6 are then fastened together with a piece of thread wound on them in the lengthwise direction of the flask, as shown in Fig. 7, and then inserted into the bottom of the flask holder 8 (see Figs. 8 and 11) and the whole is then wedged into the bottom of part 11 of Fig. 8, the above described base and flask and their contents replacing the base and flask and contents shown in Fig. 8; part 11 is then fitted against the top for fastening this flask in the bottom of the part 11 of Fig. 8 in this way all or any one i or more of my improvements excepting that pertaining to pressure casting may be applied to the operations with this flask and the flasks shown in Figs. 8, 12, 14, 16 and 17, or any other flasks used for making castings in a one piece mold; or to operations whereby aone piece unflasked mold is made and used to produce a casting. For making thin castingslike leaves of plants or petals of flowers the mold used should be about as hot at the time of casting as the fusing point of the metal cast therein.

In the foregoing operations instead of mounting the object on the end of the wire with wax the object may be stuck on the sharp pointed end of a piece of wire as shown in Fig. 18, or in the split in the split end of a piece of wire as shown in Fig. 19; and the other end of the piece of wire stuck into the hole 3 in the turnable ball part 4 of one of the bases shown in Figs. 15 and 22.

The apparatus shown in Fig. 20 may be used instead of the apparatus shown in Fig. 8, in this case the pattern, base 5, flask 6 and the rings 51 and 52 thereto attached are placed in the lower compartment 37 as shown, then the freshly preparedmold mixture is poured into the upper compartment 36 and the air exhausted from the upper and lower compartments 36 and 37, and the stirrer 42 rotated to thoroughly mix and keep mixed the ingredients of the mold mixture and free it from bubbles of rarefied air and froth, after a brief stirring of the mold mixture the stopper 43 is drawn up into the upper compartment 36 by lifting on the external partof the stirrer 42 thus opening the passage 38 and causing the mold mix- 52 and the base 5.

The apparatus shown in Fig. 21 is like that shown in Fig. 20, and used to invest objects in fourseparate flasks from one preparation of the mold mixture at one pouring: by closing the cock 49 this apparatus can be operated so as to exhaust only the lower compartment 37 then the air separates from the mold mixture as it flows through the vacuum in the lower compartment between the passage 38 and the flasks 6. The stopper 43 in this figure is broken away to show a conventional swivel joint connecting the stopper 43 and the stirrer 42 so that rotation of the stirrer does not rotate the stopper while the passage 38 is closed.

In case the object is mounted on the base 5 by thrusting the stem 79 of it into the hole of the elastic ball 54 as shown in Figs. 14 and 22 it is desirable to have a hollow handle 55 on the lower side of the ball 54 to aid in adjusting it in the flask, such a handle is shown in Figs. 14 and 22.

Having thus described my invention, I claim as new and desire to secure by Letters Patent the following:

1. In the process of reproducing destruetible objects by casting the step of soaking the object in a liquid which dissolves out the ash forming ingredients.

2. In the process of reproducing destructible objects by casting the steps of soaking the object in a. first liquid to dissolve out part of the ash forming ingredients, then in a second liquid to dissolve out other ash forming ingredients not soluble in the first liquid.

3. In the process of reproducing destruetible objects by casting the step of applying a melted destruetible substance to the object for the purposes of making both the objects and the castings obtained therefrom thicker and stronger.

4. In the process of reproducing destruetible objects by casting the steps of exhausting the air from the space containing the oe ect and the mold mixture, then investing the object in the mold mixture and admitting the air to the space over the mold mixture before the mold mixture solidifies.-

5- In the process of reproducing destructible objects by casting the steps of investing the object in a mixture of water and other suitable materials to form a refractory and porous mold, then exhausting the air from the mold mixture and the space containing the meld mixture, and returning the air to the space over the mold mixture before the mold mixture solidifies.

6. In the process of reproducing destruetible objects by casting the step of forcing a melted-metal from the funnel of the flask into the cavity left by destroying the object by means of gaseous pressure applied to the exposed part of the surface of the metal and thereby driving a part of the metal into the cavity and leaving the remainder sealing the part of the surface of the mold not covered y the flask.

7. A process of reproducing destruetible objects by casting consisting in soaking the object in a liquid which dissolves out the ash forming ingredients, applying a melted deside of the thick inside flange of the collar 13 (Figs. 8 and 9) and a quantity of a suitable mold mixture 14 is next prepared in the lower part 11, this art is next fitted against the underside o? the inside flange of the collar 13; and the receiver 12 thus formed is exhausted of air by the operation of a Vacuum pump 23, a gage 22 indicating the degree of exhaustion (see Fig. 10) The production of a vacuum over the mold mixture 14 causes the air to separate therefrom in bubbles of rarefied air which rise and form a froth thereon; this froth is quickly destroyed by agitating the mold mixture in any convenient way such as by shaking; one

' Way is to vibrate the lower part of the receiver like a pendulum while holding it so that the pattern is in or near the axis of the vibration. The receiver 12 is next turned over, keeping the tube 15 on the upper side and set down on the end containing the pattern, thus causing the mold mixture 14 to flow into and fill the flask and envelop the pattern. Air is then admitted to the receiver 12 by opening the stop cook 27 (shown in Fig. 10). The parts of the receiver 12 are next separated and the flask holder 8 and its contents are removed from part 11. After the mold thus formed has solidified, the combined flask and base and their contents are removed from the flask holder 8 by peeling back the tongues 10 between the slits (these are shown in Fig. 11) and then taking hold of the flask and pulling it out of the holder 8. Any mold material extending above the end of the flask is pared off, the thread 7 (see Fig. 7 is unwound and the base 5 removed from the flask 6 leaving the mold 6" (Fig. 6) therein. The piece of wire is withdrawn from the mold with the base 5, or separately before or afterward, to leave the sprue here shown as containing the gate 2 of Fig. 6; a little of the mold is pared away inside of the end of the flask G as shown in Fig. 6 to form a clearance between the bottom of the mold and the plate 34. The purpose of conducting the operation of investing the pattern with the mold mixture in a vacuum is to prevent air bubbles from adhering to the pattern and finally causing protuberances on the casting.

The mold (Fig. 6) is next dried, and then the flask and mold are heated sufliciently to cause the object to burn out and leave a like shaped cavity inthe mold; then While the mold is hot it is seated on the plate 34 over the hole 35 of the suction head (shown in Figs. 6' and 12) with the cup end (5 down and the funnel end 6 up. A quantity of metal, such as gold, silver, brass or aluminum, suflicient to make the cast ing 1. the gate 2 and the button 6 of Fi 6, is placed in the funnel 6 of the flas 6 of Fig. 6 and melted by the flame of a blow torch, or other suitable means, which is brought to bear upon it, then the cook 33 is o ned connecting the space between the bottom of the mold 6 with an exhausted vacuum chamber (not shown) this makes a vacuum in the ores and cavity of the mold so that the me ted metal is forced into the cavity of the mold by the pressure of the outside air upon the body of melted metal in the button 6, the gate 2 and the casting 1; in this operation the melted metal button 6 forms a liquid seal over the small part of the mold in the opening in the bottom of the funnel 6 of the flask 6 and thus prevents any air from entering the mold 6" from the top or elsewhere and permits an equal exhaustion of the gas from the pores in all parts of the mold 6', thus causing the melted metal in the casting 1 and the gate 2 to exert an equal pressure toward all of the surface of the mold cavity during the time of the change from the fluid to the solid st-ate. To remove the casting 1 the mold 6* is disintegrated, then the button 6 will drop out far enough from the bottom of the funnel 6 so that the gate 2 can be reached and the button 6 cut ofl with a pair of shears, or otherwise.

Fig. 13 is a modified form of the flask 6 of Fig. 6 suitable for use with the ring 30 instead of the flask shown in Fig. 12, it has an outside flange 6 near the top which seats against the top of the ring 30 of Fig. 12, the bottom of this ring seats against the top side of the plate 34 over the central hole 35; this flask has a plurality of holes 6 through the wall of the cup 6; these holes promote the drying of the mold and furnish additional openings for the escape of gas from the pores and cavity of the mold in the operation of making a vacuum casting therein; for these purposes the holes are about as large and numerous as the strength of the wall of the cup 6" will permit them to be made.

The flasks shown in Figs. 6 and 13 are composed of such materials as are used for making crucibles.

Another way to operate the apparatus shown in Figs. 6, 7, 8, 9, 10 and 11 is to assemble the contents of part 11 as shown in Fig. 8, keeping the open end of part 11 up, and pour the mold mixture into the flask 6 and the flask holder 8, then fit the collar 13 and the part 11 over the part 11 and ex haust the air from the receiver 12 thus formed, then by shaking the device horizontally destroy the froth on the mold mixture. In this way of operating the open end of the part 11 is kept up throughout the operation, and the part 11 serves only as a lid. The receiver and contents are dismembered in the same way as in the previously described operation in which the receiver is turned over.

Other forms of bases, flasks and molds hausting the air from ,the space containing the object and the mold mixture, then investing the object in the mold mixture and admitting air to the space over the mold mixture before the mold mixture solidifies, drying the mold thus formed, then heating the mold and thereby causing the object to burn out and leave a like cavity in the mold, forcing a melted metal from the funnel of the flask into the cavity left by destroying the object by means of gaseous pressure applied to. the exposed part of the surface of the metal and thereby driving a part of the metal into the cavity and leavin the remainder sealing the part of the surface of the mold not covered by the flask, and then removing the material of the mold from the casting.

8. A process of reproducing destructible objects by casting consisting in applying a melted destructible substance to the object for the purposes of making both the objects and the castings obtained therefrom thicker and stronger, mounting the object in a flask, exhausting the air from the space containing the object and the mold mixture, then investing the object in the mold mixture and admitting air to the space over the mold mix ture before the mold mixture solidifies, drying the mold thus formed, then heating the mold and thereby causing the object to burn out and leave a like cavity in the mold, foreing a melted metal from the funnel of the flask into the cavity left by destroying the object by means of gaseous pressure applied to the exposed part of the surface of the metal into the cavity and leaving the remainder sealing the part of the surface of. the mold not covered by the flask, and then removing the material of the mold from the casting.

9. A process of reproducing destructible objects by casting consisting in soaking the object in a liquid which dissolves out the ash forming ingredients, mounting the object in a flask, exhausting the air from the space containing the object and the mold mixture, then investing the object in the mold mixture and admitting air to the space over the mold mixture before the mold mixture solidifies, drying the mold thus formed, then heating the mold and thereby causing the object to burn out and leave a like cavity in the mold, forcing a melted metal from the funnel of the flask into the cavity left by destroying the object by means of gaseous pres sure applied to the exposed part of the surface of the metal and thereby driving a part of the metal into the cavity and leaving the remainder sealing the part of the surface of the mold not covered by the flask, and then removing the material of the mold from the casting.

10. A process of reproducing destructiblc objects by casting consisting in mounting the object in a flask, exhausting the air from the space containing the object and the mold mixture, then investing the object in the mold mixture and admitting air to the space over the mold mixture before the mold mixture solidifies, dryin the mold thus formed, then heating the mo d and thereby causing the object to burn out and leave a like cavity in the mold, forcin a melted metal from the funnel of the flask into the cavity left by destroying the object by means of gaseous pressure applied to the exposed part of the surface of the metal and thereby driving a part of the metal into the cavity and leaving the remainder sealing the part of the surface of the mold not covered by the flask, and then removing the material of the mold from the casting.-

11. In the process of reproducing destructible objects by casting the steps of soaking the object in a liquid Which dissolves out the ash forming ingredients, applying a melted destruotible substance to the object for the purposes of making both the objects and the castings obtained therefrom thicker and stronger, exhausting the air from the space containing the object and the mold mixture, then investing the object in the mold mixture and admitting air to the space over the mold mixture before the mold mixture solidifies.

12. In the process of reproducing destruc tible objects by casting the steps of apply ing a melted destructible substan'ce to the object for the purposes of making both the objects and the castings obtained therefrom thicker and stronger, exhausting the air from the space containing the object and-the mold mixture, then investing the object in the mold mixture and admitting air to the space over the mold mixture before the mold mixture solidifies.

13. In the process of reproducing destructible objects by casting the steps of soaking the object in a liquid which dissolves out the ash forming ingredients, exhausting the air from the space containing the object and the mold mixture, then investing the object in the mold mixture and admitting air to the space over the mold mixture before the mold mixture solidifies.

14. In the process of reproducing destructible objects by casting the steps of soaking the-object in a first liquid to dissolve out part of the ash forming ingredients, then in a second liquid to dissolve out other ash forming ingredients not soluble in the first liquid, exhausting the air from the space containing the object and the mold mixture, then investing the object in the mold mixture and admitting air to the space over the mold mixture before the mold mixture solidifies.

15. A process of reproducing destructible objects by casting consisting in soaking the object in a liquid which -dissolves out the ash forming ingredients, applying a melted destructible substance to the object for the purposes of making both the objects and the castings obtained therefrom thicker and stronger, mounting the object in a flask, investing the object in a mixture of Water and other suitable materials to form a refractory and porous mold, drying the mold thus formed, then heating the mold and thereby causing the object to burn out and leave a like cavity in the mold, forcing a melted metal from the funnel of the flask into the cavity left by destroying the object by means of gaseous pressure applied to the exposed part of the surface of the metal and thereby driving a part of the metal into the cavity and leaving the remainder sealing the part of the surface of the mold not covered by the flask, and then removing the material of the mold from the casting.

16'. A process of reproducing destruetible objects by casting consisting in applying a melted destructible substance to the ob ect for the purposes of maln'ng both the objects and the castings obtained therefrom thicker and stronger, mounting the object in a flask, investing the object in a mixture of water and other suitable materials to form a refractory and porous'mold, drying the mold thus formed, then heating the mold and thereby causing the object to burn out and leave a like cavity in the mold, forcing a melted metal from the funnel of the flask into the cavity leftby destroying the obj ect by means of gaseous pressure a plied to the exposed part of the surface of 51c metal and thereby driving a part of the metal into the cavity and leaving the remainder sealing the part of the surface of the mold not covered by the flask, and then removin the material of the mold from the casting.

17. A process of reproducing destructible objects by casting consisting in soaking the object in a liquid which dissolves out the ash forming ingredients, mounting the object in a flask, investing the object in a mixture of Water and other suitable materials to form a refractory and porous mold, dryin the mold thus formed, then heating the mol and thereby causing the object to burn out and leave a like cavity in the mold, forcing a melted metal from the funnel of the flask into the cavity left by destroying the object by means of gaseous pressure applied to the exposed art of the surface of the metal and thereby riving a part of the metal into the cavity and leaving the remainder sealing the part of the surface of the mold not covered by the flask, and then removing the material of the mold from the casting.

18. In the process of reproducing destructible objects by casting the steps ofsoaking the object in a liquid which dissolves out the ash formin ingredients, and applying a melted destructible substance tothe ob ect for the purposes of making both the objects and the castings obtainedtherefrom thicker and stronger. v ROBERT J. DAVIDSON.

' Witnesses: R. M. LAWRENCE S O 

